The utility man's second-half effort helped The Eagles claim all three points on offer at Selhurst Park.
The goal was his fourth in 22 topflight matches, involving 10 starts, so far this season.
Luka Milivojevic put Palace in front with a 25th-minute penalty after Cyrus Christie was adjudged to have handled the ball in the box.
Three minutes to full-time, Schlupp sealed the win with the second goal, tapping home a rebound after goalkeeper Sergio Rico parried Michy Batshuayi's strike.
The result leaves The Eagles on 14th position on the table, while Fulham sit one place above the bottom spot.
Schlupp lasted for the entire duration of the game, while compatriot and club-mate Jordan Ayew was substituted in the 82nd minute.